how to do custom animation in a mhx file made using Makehuman
You should read or watch a few of the available tutorials or 100 'best', the mhx addon adds buttons for the rig-layers where you can select which manipulators are shown in the viewport.
The following animation was recorded in Pose Mode. You should read about the difference between IK/FK.
After that just record your animation by keyframing the poses setup by the controls.